1. Field of the Invention
The invention is related to the field of communications and, in particular, to systems and methods for charging element capacity control in IMS networks.
2. Statement of the Problem
One type of communication network gaining popularity is an IP Multimedia Subsystem (IMS) network. As set forth in the 3rd Generation Partnership Project (3GPP), IMS provides a common core network having access-agnostic network architecture for converged networks. Service providers are accepting this architecture in next generation network evolution. The IMS architecture is initially defined by the 3GPP to provide multimedia services to mobile subscribers over an Internet Protocol (IP) network. IP networks have become the most cost savings bearer network to transmit video, voice, and data. IMS uses the advantage of IP networks to provide multimedia services for IMS subscribers on an IMS platform. The signaling used within IMS networks is Session Initiation Protocol (SIP). IMS defines the standard SIP interface between application servers, the IMS core network (CSCF), the IMS subscriber, the IMS database (HSS), and IMS charging elements. These standards can reduce the network integration costs and let the subscriber enjoy more stable services.
Examples of IMS charging elements include a Charging Collection Function (CCF) as defined by the 3GPP Release 5 or a combination of Charging Data Function (CDF) and Charging Gateway Function (CGF) as defined by the 3GPP Release 6. A CCF or a CDF receives call measurement data and charging information from a plurality of network nodes serving an IMS call, then generates Charging Data Records (CDR) and transmits the CDRs to a billing system. The CCF or CDF also processes the call measurement data and charging information to derive network traffic and performance information which is forwarded to a network management system operated by the service provider. In such manner, the service provider can monitor the traffic flows and system performance associated with the charging elements.
The charging elements are typically engineered to accommodate traffic flows not exceeding a stated (or “engineered”) capacity; and the service provider will generally provision/purchase charging equipment based on the engineered capacity to accommodate expected network traffic. (For this reason, the term “purchased capacity” is often used synonymously with the stated or engineered capacity.) The service provider can configure alarms to be generated to the network management system when the traffic flows approach or exceed the purchased capacity. Responsive to such alarms, the service provider at its discretion may reduce traffic or shut down the charging elements to prevent overload of the charging elements and to maintain system performance. However, it is also within the service provider's discretion to push the charging equipment beyond its purchased capacity and/or to configure no or low level alarms to the network management system when approaching or exceeding the purchased capacity. If this occurs, there is presently no mechanism for the equipment vendor/seller to control, monitor or collect revenue for the overload on charging elements relative to the purchased capacity.